The conventional technique of the circuit-pattern inspection device is explained using the inspection of a semiconductor wafer as an example. The semiconductor device is produced by repeating the step of transcribing the circuit pattern formed on a photo mask onto the semiconductor wafer through lithography and etching processes. In the process of semiconductor device production, the quality of lithography and etching process and the generation of foreign material can significantly affect the yield of semiconductor devices. Thus in order to detect faults and abnormalities in the production process at an early stage or in advance, various devices (circuit-pattern inspection devices) are used to inspect defects in the circuit patterns over the semiconductor wafer during the production process.
Commercialized circuit-patter inspection devices include an optical defect inspection device that irradiates the semiconductor wafer with light to compare the same kind of circuit pattern between plural LSIs using optical images, and an electron beam defect inspection device that irradiates the semiconductor wafer with charged particle beam, such as an electron beam, to detect secondary or reflected electrons emitted from the radiated wafer before turning the detection signal into images, thereby detecting defects.
The electron beam defect inspection device performs defect inspection by comparing SEM (scanning electron microscope) images. There exist two methods for obtaining SEM images: the method of obtaining the images by moving a stage in a stepped and repeated manner and by scanning an electron beam two-dimensionally at each position where the stage is stopped, and the method of obtaining the images continuously by shifting the stage in a scanning movement at a constant velocity in a given direction while simultaneously applying an electron beam for scanning one-dimensionally in the direction of stage movement and in the vertical direction. Most electron beam defect inspection devices utilize the latter method that offers better throughput. Non-Patent Literature 1, Non-Patent Literature 2, Patent Literature 1, and Patent literature 2 below disclose a method for irradiating a conductive substrate with an electron beam at least 100 times as intense (10 nA or higher) as that of the ordinary SEM, detecting secondary, reflected, or transmitted electrons emitted from the substrate, and comparing and inspecting images between adjacent same patterns formed by the signal of detected electrons.